This protocol describes a study designed to test the hypothesis that treatment with OPC-14117 ( a neuroprotective agent and cognitive enhancer) prevents central nervous system dysfunction following cardiopulmonary bypass surgery. Three groups of 21 subjects will be studied; one group on placebo, a second on 60mg/day and a third on 120 mg/day of OPC-14117. The study will be conducted as a randomized, double blind, placebo-controlled design. QEEG data will be collected one week prior to and during surgery.